The show has given us almost nothing about Earth. I can come up with interesting stories, but they are not based on what we see in the show. In fact, we were told at the start that they never get to Earth, but they may have changed their minds on that, and since it seems Starbuck has come here, that in some sense it's already false.

From clues in the show, I think it's pretty clearly in our distant future. And yes, Starbuck's visit says its not dead, and that the beings who took Starbuck are probably from Earth or related to it. But we also have the prophesy that Starbuck will lead the human race to its end, and alas, my thought that this just means "goal" is probably wrong based on the writer's meeting podcast.

The key thing is how to make reaching Earth satisfying. By all rights, Earth should be a planet of vastly advanced beings, which make it hard to avoid a deus ex machina ending. "Welcome to Earth, all is happy now" would be dull. There must be conflict. One can have that if there are two opposing powerful forces, but there is a limit to how much you can involve the humans (or cylons) in a war of the gods. Yes, BSG Classic did that in its way, but it's hard to make a satisfying ending where the mortals played a meaningful role.

So a more likley scenario is Earth reveals the big mysteries, so we don't mind the sappy "all is happy" ending.